1. Field of the Invention
This invention is applicable to a computer-aided design (CAD) system utilizing an information processing system. This invention relates to a system for retrieving three dimensional graphic information stored in a data base and originally was developed for designing bottle shapes but can be used to design other types of three dimensional objects.
2. Description of Related Art
As the technology of the CAD system has advanced in recent years, CAD systems have been developed which display, on a CRT display unit screen, a plan view of a three dimensional object defined by three dimensional graphic data input into the system. These systems are further capable of automatically adjusting the graphic data pertaining to the views of the object that are not displayed (e.g. back view, side views, etc.) based on alterations of the plan view displayed on the CRT display screen. In such a system, when a plan view of a shape is displayed on the screen of the CRT display unit and altered by an input device (e.g., a "mouse"), the related alterations automatically are made by the computer on the right and left side views, bottom view and top view. Some systems are designed to instruct users to input data in addition to the data relating to the plan view to achieve fully corrected and complete data relating to the entire three dimensional object.
Alternatively, a method for using a CAD system as described above has been proposed wherein many sets of graphic data are stored in a database. When a new shape is to be designed, stored graphic data relating to a desired shape image is read out from the data base and displayed on the CRT unit as the basic shape to be partially revised or modified by the operator. A method also has been proposed wherein a plurality of shape images, defined by graphic data stored in the database, are displayed on the screen of the CRT display unit simultaneously. The operator can set the positions and dimensions of each shape arbitrarily via an operation terminal and combine these shape images into one. These methods are excellent in reducing the number of steps in the design process.
In the CAD systems described above, it is preferable to store in the database information relating to a sufficiently large number of shapes and effectively select and retrieve out of the database the information relating to a shape which most resembles the desired shape. It is further preferable to reduce, as much as possible, the revisions or modifications of the existing shapes needed to form the new shapes in order to reduce the number of steps required for designing the new shapes. That is, if a basic "stored" shape better approximates the new shape which a designer desires, he/she can use the basic shape to design the new shape more easily.
Therefore, it is essential for the CAD system to be capable of retrieving, out of the large number of graphic data sets relating to a large number of shapes stored in the database, a basic "stored" shape most approximate to the desired shape. If the basic stored shape is simple, it can be identified by name such as a "circle" a "square" or a "rectangle" and thus retrieved by name. When the number of stored shapes is small enough to be coded by their characteristics, they can be retrieved by this characteristic code and an operator may display these stored shapes individually on the CRT display unit. The operator then may select one of these shapes for modification.
Several problems exist with a CAD system as described above which identifies the shapes by their named characteristic (e.g. "square"). For example, the number of existing bottle shapes is enormous (for instance, several thousands), and these shapes are not given names. If the graphic data sets relating to each of these large number of shapes is stored in the database, an operator using the above CAD system to design a new bottle shape from the existing shapes may waste much time retrieving each of these shape images from the database and displaying them individually on the display screen. Moreover, because the stored data relates to three dimensional shapes, it is not always possible to display the three dimensional image on the two dimensional screen accurately. Therefore, the designer/operator may view the image incorrectly and select an undesired image by mistake.